Some types of acidic liquids, like folic acid and citric acid, are important nutrients for dietary health. Acids can also be damaging to your tooth enamel. The acids present in sodas, for example, can erode the protective outer layers of the tooth leading to decay. Acidic liquids will interact with basic liquids in ways that may spoil food. The acids in tomatoes, for instance, will curdle milk, making it necessary to add another basic ingredient--such as baking soda--before adding the milk to make cream of tomato soup.
Citric acid is a weak dietary acid used as an additive in many foods for flavoring or as a preservative. Most commonly, citric acid is found in the liquids of citrus fruits, such as oranges or lemons. Lemon juice is very high in citric acid, lending to its sour flavor. Citric acid is also added to sodas as a preservative. While citric acid is relatively benign, excessive consumption should be limited, according to dentist Dr. Nancy Rosen. This is because citric acid can erode tooth enamel, subjecting the tooth to decay, sensitivity and discoloration.
Folic acid is also known as vitamin B9, and is an important dietary nutrient particularly for pregnant women. Folic acid contributes to cellular genesis, and its deficiency is linked to birth defects in the brain and spine. It is present in the liquids of leafy green vegetables such as spinach, peas, beans and nuts. Folic acid is also an additive in certain fortified grain products, such as pastas and breads. Some cereals contain up to 100 percent of the FDA's recommended daily allowance of folic acid, but individuals who do not receive enough in their foods can also take a folic acid supplement.
Ascorbic acid, also known as vitamin C, is an antioxidant linked to the prevention of heart disease, high blood pressure, osteoarthritis, macular degeneration and asthma. It is best known for its role in strengthening the immune system, and is often an ingredient in supplements used to battle the common cold. Though orange juice and other citric juices are a common source of ascorbic acid, foods such as watermelon, strawberries, broccoli and cabbage are also rich in ascorbic acid. A vitamin C deficiency is linked with the disease scurvy, hence the name ascorbic acid: "a-" meaning not, and "scorbutus" meaning scurvy.